1. Technical Field
The present invention relates to the repair of bone fractures, in particular, the present invention relates to a method and system for the computer assisted repair of bone fractures.
2. Discussion of the Related Art
Generally, in repairing bone fractures, the bone must be reduced. Reduction is a medical procedure to restore a fracture or dislocation to the correct alignment. When a bone fractures, the fragments lose their alignment in the form of displacement or angulation. For the fractured bone to heal without any deformity the bony fragments must be re-aligned to their normal anatomical position. This repositioning step is generally the most difficult, since it is difficult for the surgeon or physician to appreciate how to precisely orient the portions of the fractured bone. For example, in the case of a long bone single fracture, two bony fragments are generated and are generally repaired with a nail (or external plate or pin), that for example may enter the medullar cavity of the bone. The nail (or plate) is then attached to the distal and proximal ends of the bone by screws. In the specific case of the femur, the nail is typically introduced into the medullar cavity through the proximal end and then attached to the distal end.
A conventional method for assisting surgeons before and during the reduction of a fracture includes the use of two-dimensional images such as fluoroscopy image data. Based upon the fluoroscopy data, the surgeon can perform the necessary reduction to reposition the bony fragments or elements. Once the bony fragments have been properly positioned and nailed, additional fluoroscopy images are obtained to facilitate placement of nail attachment screws.
The article entitled: “FRACAS: A System for Computer-Aided Image-Guided Long Bone Fracture Surgery” by Joskowicz et al., Comp. Aid Surg. 1999; 3(6):271-288, describes a computer-assisted method for the reduction of a fracture for a long bone that includes the steps of; forming a three-dimensional model, for example, by tomography data, of the external surface of a healthy bone, for example a femur bone, to assist the surgeon in the selection of the length and of the diameter of the nail to be used to connect the portions of the fractured bone, forming three-dimensional models, also by tomography data, of the external surfs of the proximal and distal portions of the fractured bone, tracking the positions of the proximal and distal portions with a three-dimensional positioning system, readjusting the models of the proximal and distal portions in accordance with the positions of the proximal and distal portions of the fractured bone obtained by fluoroscopy, tracking in real time on a screen images representative of the proximal and distal portions manipulated by the surgeon to assist him in the repositioning of the proximal and distal portions; and forming a new set of two-dimensional images by fluoroscopy to check the relative positions between the proximal and distal portions to insert an attachment nail.
The method described in article “FRACAS” has the advantage of decreasing the number of images to be acquired by fluoroscopy since the tracking of the displacements of the osseous portions is performed based on previously-determined three-dimensional models. However, such as method requires a pre-operative study to form the three-dimensional models by tomography. Further, the acquisition of images by radiation based imaging (i.e., fluoroscopy) is not completely eliminated.